A responsive website is the need of the hour. Your customers expect it and delivering one gives you the bonus of ranking higher in Google SERPs(Search Engine Result Pages).
In the current age of digitalization, people are driven towards digital discovery through a mobile-first approach. Keeping that in mind, web developers from big enterprises as well as small businesses, make a note of optimizing a website as mobile-friendly as possible.
It is important for a website to be optimized in such a manner that it gets rendered properly in various mobile devices. Even if you are creating a new website, instead of developing a separate one for mobile users it is ideal to create a responsive website that fits properly in all kinds of devices.
A good old way to check the responsive for different screen sizes would be to drag any corner of the browser window. As you reduce the browser window you can have an estimate of how responsive is your website.
If you want to get rid of the estimation and give a thorough check of RWD with respect to various media queries then I would suggest you use a cross browser testing tool. A cross browser testing cloud would help you evaluate your RWD with live interactive sessions through different screen sizes. You can capture automated screenshots in bulk for various mobile devices. Plus the integrations offered would help you log a bug with colleagues in a much simpler manner. You can hasten your release process for good.